To characterize the beam from a high power laser, it is necessary to isolate atmospheric distortions of the beam while operating the laser at full output power. To keep the transmitted beam intensity below the threshold for atmospheric disturbances, a hole grating or beam attenuator is used. These techniques are now well developed for this type of measurement and can be found in most textbooks on optics such as Principles of Optics by Max Born and Emit Wolf.
For high power cw lasers such as the GDL (gas dynamic lasers), a low transmission (.apprxeq.4%) cooled hole grating is used to attenuate the beam. For high power pulsed lasers operating in the single pulsed mode, a high transmission hole grating made from wires has been found to be useful. In this case the intensity distribution is measured in one of the higher orders of the diffraction patterns.
It is an object of this invention to supply a device which allows for the measurement of the intensity distribution of each pulse in the pulse train from a high power laser.
It is an additional object of this invention to supply a technique for positioning each grating in the laser beam at the appropriate time.